The present invention relates to hydraulic shock absorbers, and more particularly, to a shock absorber of the double-acting tubular type having an improved mechanism for adjusting the compression forces in the shock absorber. The shock absorber is especially useful on vehicles such as snowmobiles.
Double-acting shock absorbers utilized on vehicles usually comprise an inner or working cylinder attached, at one end and through an end cap, to the unsprung mass of the vehicle; and a piston that is movable within the inner cylinder, that has a piston rod extending out of the other end, the rod end, of the inner cylinder, and that is connected with the sprung mass of the vehicle, via the piston rod, so that when the vehicle passes over an uneven surface, the piston and inner cylinder move relative to one another. The inner cylinder contains suitable hydraulic damping fluid that may be transferred across the piston by means of valving in the piston. During the so called compression stroke of the shock absorber, that is, when the axle and frame move toward one another, a relatively small amount of the fluid is expelled from the one end of the cylinder into a reservoir which is, conventionally, an annular space defined between the inner cylinder and a surrounding outer cylinder.
The flow of fluid expelled from the cylinder during a compression stroke is typically controlled by a compression valve positioned in the compression head assembly of the shock absorber. The compression valve is normally spring biased to a closed position. During the compression stroke, fluid pressure increases in the cylinder. When the fluid pressure reaches a predetermined level, the pressure overcomes the spring load or bias on the compression spring, causing the compression valve to open and allowing fluid to flow from the inner cylinder into the reservoir.
It is known in the art that the compression forces of the shock absorber are dependent upon the load or tension on the compression valve spring. By adjusting the tension on the compression valve spring, it is possible to adjust the compression forces of the shock absorber and thereby adjust the ride or feel according to snow or road conditions so as to achieve user satisfaction.